34 Rockwell Automation Publication 440R-UM012E-EN-P - November 2018
Chapter 6 Pulse Testing Functions
Pulse Testing for Inputs
When configuration starts with Logic Switch setting 9 and goes to a setting
from 1 to 4, X14 and X24 terminals generate quick pulses that are used to test
for short circuit conditions. This configuration is ideal for guard locking
interlocks with mechanical contacts. It is required to achieve a Cat. 4 safety
performance rating.
X14 is connected through one mechanical contact to S12 or S22 and X24 is
connected through the other mechanical contact to S22 or S12.
Figure 26
shows a typical sequence of test pulses. The individual transistor tests
are interspersed between the main transistor tests.
Figure 26 - Pulse Test Sequence
Test of OSSD Outputs
The GLP safety relay does not use pulse testing when X14 and X24 are
configured as OSSD outputs. Instead, the GLP safety relay turns the OSSD
outputs with a short delay between them. If a cross fault short circuit exists
between X14 and X24, the GLP safety relay detects that condition and
immediately turn the outputs OFF. Turn OFF occurs in less than 1 ms and the
PWR/Fault status indicator flashes red six times.
Figure 27 - OSSD Cross Fault Detection
TIP • X14 can be connected to S12 or S22
• X24 can be connected to either S12 or S22
X24
X14
erminal
24V
0V
24V
0V
0
Main Transistor Tests
Individual Transistor Tests
X24
X14
Terminal
24V
0V
24V
0V
0
500…1000 µs
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